Liquid crystal displays are expanding the range of their uses year after year because of their low power consumption and high space-saving rate as image display devices. Although great viewing-angle dependence of images and slow display response were major drawbacks to liquid crystal displays in the past, fast-response VA mode liquid crystal display models with wide viewing angles have recently been commercialized, and thereby the demand for liquid crystal displays is rapidly growing even in the market requiring high-quality images, such as the TV-set market. With this growing demand, further improvement in optical compensating power has been required for optical compensation members used in liquid crystal displays for the purpose of improving hue, contrast and viewing-angle dependences of these factors.
With respect to optical compensation films for VA mode liquid crystal displays, it is known that a combination of A-plate and C-plate compensation films in particular has a highly improving effect on viewing-angle dependence of contrast.
Further, WO 2004/068226 discloses the art of performing optical compensation by use of polymer films differing in wavelength dispersion between in-plane retardation and retardation in the direction of thickness (hereinafter referred to as thickness-direction retardation), thereby further improving the contrast and bringing the hue in black display close to gray.
However, such an art is insufficient to produce an effect of reducing viewing-angle dependence of hue, so improvements in this point have been required.
With respect to the birefringent films whose in-plane retardation and thickness-direction retardation are controlled, there are known the method of stretching a cellulose acylate film to which a retardation developing agent is added (JP-A-2002-192541) and the method of deforming a polymer substrate coated with a polymer capable of aligning (JP-A-2003-344657). However, such methods pose limitations to the range of retardation control and are insufficient in point of hue changes by viewing angles.